Increasingly, many industries and industrial processes require a very high purity of oxygen in their processes and manufacturing systems. Due to today's more stringent purity requirements in, for example, the electronics industry, many existing production processes for oxygen separation from air may not be sufficient to produce consistent quantities of ultra-high purity oxygen gas. For uses requiring a purity in the parts-per-billion range, fractional distillation with even a very high number of stages may not be sufficient to provide ultra-high purity oxygen product.
Existing processes to produce ultra-high purity industrial gases often employ braised aluminum heat exchangers within the cryogenic columns. Such braised aluminum heat exchangers typically comprise many welds which by their very nature are susceptible to permeation between fluids and are, therefore, a risk for a source of potential contamination in the ultra-high purity product. An alternative to braised aluminum heat exchangers would be stainless steel shell and tube heat exchangers. However, the shell and tube exchangers would also necessarily contain welds which would also be susceptible to leaks of one fluid to the other.
Avoiding harmful permeation between dissimilar fluids and the resulting contamination of an ultra-high purity product of an air separation process is a substantial problem requiring a new solution.